Method and device for operating an internal combustion engine

Abstract

A method and a device for operating an internal combustion engine are provided, which allow a continuous limiting of the output of the internal combustion engine upon attaining a maximally possible injection duration of an injection valve. The internal combustion engine has at least one actuator for influencing the output of the internal combustion engine and at least one injection valve for supplying fuel to the combustion engine. A maximally possible injection duration for an injection procedure of the at least one injection valve is determined. A variable characterizing the output of internal combustion engine is limited as a function of the maximally possible injection duration by corresponding adjustment of the at least one actuator.

Description

FIELD OF THE INVENTION[0001]The present invention relates to a method and a device for operating an internal combustion engine.BACKGROUND INFORMATION[0002]It is already known that the available time for an injection of fuel into a combustion chamber of an internal combustion chamber is limited. In systems where an injection takes place in front of the intake valves of the combustion chamber, the entire injection must be concluded before the individual intake valve closes. The injection for the next aspiration of the cylinder may then begin. In direct gasoline injection, the injection begins after the intake valve has been closed, but must be concluded prior to ignition. The maximum injection duration gets shorter with increasing engine speed. Injection valves are therefore designed such that they are able to discharge the required injection quantity even at maximum rotational speed and full loading of the internal combustion engine. They are tightly configured so that fuel is able t...

AI Technical Summary

Benefits of technology

[0003]In contrast, the method according to the present invention as well as the device for operating an internal combustion engine according to the present invention, have the advantage of ascertaining a maximally possible injection duration for an injection operation of the at least one injection valve, and of limiting a variable characterizing the output of the internal combustion engine by a corresponding adjustment of the at least one actuator as a function of the maximally possible injection duration. This ensures compliance with the maximally possible injection duration without sudden drop in the output of the internal combustion engine at full load and with a required enrichment of the air / fuel-mixture ratio, for instance. In this manner a steady limiting of the output of the internal combustion engine is able to be implemented once a maximally possible injection duration of an injection valve has been reached.

[0004]It is particularly advantageous if a maximally possible air charge in a combustion chamber (20) of internal combustion engine (1) is ascertained as a function of the maximally possible injection duration and a predefined air / fuel mixture ratio as a variable characterizing the output of internal combustion engine (1), and if the setting of the at least one actuator (5, 10) is limited as a function of the maximally possible air charge. This prevents an abrupt reduction of the charge, and a steady limiting of the charge is able to be realized instead. In an advantageous manner, the predefined air / fuel mixture ratio may already take into account an enrichment that may be required for reasons of component protection, thereby increasing the driving comfort.

[0005]It is especially advantageous if the maximally possible injection duration is ascertained as a function of the instantaneous state of the internal combustion engine, in particular from an instantaneous value of an engine speed of the internal combustion engine. In this manner, in anticipation of a full-load operating state, it is possible to specify a restriction of the air supply in a partial-load operating state already, in such a way that the maximally possible injection duration is still sufficient to realize the predefined air / fuel mixture. Abrupt shifts to lower torques in the full-load range, which interfere with driving comfort, are avoided in this manner. On the other hand, the air supply is restricted to the absolutely necessary minimum.

Problems solved by technology

On the other hand, the air supply is restricted to the absolutely necessary minimum.

Images